The present invention relates to a case for encasing a data recording medium such as a magnetic tape cassette. More particularly, the invention relates to such a case having a dustproofing structure for preventing dust and/or foreign matter from entering the case.
Conventionally, when a data recording medium such as a magnetic tape cassette is to be stored, the data recording medium is inserted in a suitable case in order to prevent foreign matter such as dust from adhering to the recording surface of the recording medium, and also to protect the cassette from damage. One example of such a case includes a closure member and a case body connected to each other through a thin hinge structure arranged such that the closure member faces the case body, whereby the closure member and the case body are able to open or close relative to each other. A frame and a peripheral wall structure are formed on opposing surfaces of the case body and the closure member at peripheral edges thereof. The frame and peripheral wall structure; which overlap with each, cooperate to define a space in which a cassette is to be stored. An engagement structure including a projection and a recess engageable with each other is provided at an overlapping area of the frame and the peripheral wall structure, thereby making it possible to keep the closure member and the case body closed relative to each other.
FIG. 1 illustrates an example of a conventional case for encasing a video cassette therein. The case 51 has a case body B and a closure member C connected to each other through a connection member J so that the case is foldable. The case body B, the closure member C and the connection member J are integrally formed of a flexible material such as synthetic resin. The case body B and the closure member C are foldable relative to each other due to a pair of thin-walled hinges 8 formed in the connection member J. In the closed position the bottom surface of the case body B faces the upper surface of the closure member C.
A rectangular frame 3 is formed on the bottom surface of a bottom plate 2 of the case body B at the peripheral edge thereof defining a space corresponding to the shape of the cassette. On the other hand, on the upper surface of an upper plate 4 of the closure member C is formed a U-shaped peripheral wall structure 5 along the front edge and left and right edges of the upper plate 4. The peripheral wall structure 5 covers or overlaps with the external surface of the frame 3 when the case is closed.
When a magnetic tape cassette T is to be encased in the case, the case 51 is opened, as illustrated in FIG. 1. Then, the magnetic tape cassette T is inserted into the case body B, and subsequently the closure member C is closed. In inserting the magnetic tape cassette T into the case body B, the magnetic tape cassette T is pressed at side surfaces thereof to thereby adjust the position of the cassette T with respect to the front, rear, left and right walls of the frame 3 defining the space in which the cassette is to be stored. Thus, it is preferable for the space for storing the cassette not to have a large gap between the frame and the cassette.
A front wall 5a, which is a part of the peripheral wall structure 5 and is disposed at the front edge of the closure member C, may be formed with projections 52, whereas a front wall 3a, which is a part of the frame 3 and corresponds to the front wall 5a of the peripheral wall structure 5, may be formed with recesses 53. By engaging the projections 52 with the recesses 53, undesired opening of the case 51 is prevented.
The frame 3 is formed at upper edges of its four walls with cut-outs 7 for ease of inserting and taking out the magnetic tape cassette T.
When the case body B and the closure member C are closed with the magnetic tape cassette T encased therein, internal surfaces of the front wall 5a and side walls 5b of the peripheral wall structure 5 overlap with external surfaces of the front wall 3a, disposed at an opening and closing distal end, and side walls 3b of the frame 3 and an internal surface of the connection member J overlap with an external surface of a rear wall 3c disposed closer to the connection member J. When the magnetic tape cassette T is to be taken out of the case, the user places his or her fingers at both edges of the bottom plate 2 and the upper plate 4, and then opens the case body B and the closure member C in the manner of a book.
In the "single swing" case 51 described above, there arises a problem in that the opening and closing operation is quite difficult when the magnetic tape cassette T is to be inserted or removed if the gap between the external surface of the frame 3 and the internal surface of the peripheral wall structure 5 is too small to the extent that the external surface of the frame 3 and the internal surface of the peripheral wall structure 5 are strongly rubbed against each other. Thus, as illustrated in FIG. 2, an appropriate gap 55a has to be provided between the external surface of the frame 3 and the internal surface of the peripheral wall structure 5 even when the case body B and the closure member C are closed relative to each other. In addition, even when the case body B and the closure member C are closed relative to each other by means of the projections 52 and the recesses 53, in order to compensate for variations in manufacturing accuracy there are unavoidably produced gaps 55b and 55c between the upper edge of the frame 3 and the upper surface of the upper plate 4, as well as between the front edge of the peripheral wall structure 5 and the bottom surface of the bottom plate 2.
However, if there is a gap 55 between the frame 3 and the peripheral wall structure 5, even when the case body B and the closure member C are closed relative to each other, foreign matter such as dust can still enter the case through a path indicated by arrows in FIG. 2. In particular, recently recording of data on a recording medium in digital form has become more common. Foreign matter adhering to the recording surface of such a recording medium may cause signal drop-out, and hence exert a more harmful effect on the reproduction of the digitally recorded data than in the case where the signal is recorded in analog form.